"Unfortunately, it appears that Carl has suffered a significant injury and he will be assessed by a specialist in central London on Wednesday," West Ham said in a statement on their website (www.whufc.com).
Jack Sullivan, son of West Ham's co-chairman David Sullivan, said on Twitter that the injury would rule Jenkinson out for the season.
"Carl Jenkinson's injury is far more serious than we thought," he said.
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(Reporting by Simon Jennings in Bengaluru Editing by Toby Davis)
